The present invention is directed to a display device having at least one light valve in particular a liquid crystal cell containing a medium which can be switched zone-wise between at least two different optical states, a light trap in the form of a plate-shaped body disposed behind the liquid crystal cell when taken in the direction of observation of the device, the body having the index of refraction greater than 1, containing fluorescent particles, and possessing outlet windows behind every switchable zone of the medium.
Display devices, which have a liquid crystal cell, and fluorescent plate, which has exit windows or emergent windows, have been described in German Offenlegungsschrift No. 26 19 368, and in U.S. Pat. application Ser. No. 747,035, issued as U.S. Pat. No. 4,142,781 and which includes the disclosure of German application No. P 25 54 226. In these devices, a fluorescent plate, which increases the representational contrast by means of fluorescent scattering and subsequent total reflection, intercepts a major part of the incoming surrounding or ambient light and passes this light finally through special light outlet windows or emergent windows with a relative high intensity.
In accordance with these previous disclosures, the outlet windows are to be constructed mainly by means of scattering pigment layers on a rear surface of the fluorescent plate or by grooves which are placed on either the rear or front surface of the plate, see U.S. Ser. No. 747,035.